A link coupling arrangement is known wherein two transmission link members are interlockably mounted on a body of a door lock assembly and one of the two transmission link members is connected to another transmitting member through a coupler member.
A link coupling arrangement as illustrated in FIGS. 8 and 9 is also known, in which the link coupling arrangement is used for a rear door lock assembly.
More specifically, a lock lever 2 and sub lever 3, which are transmission link members, are rockably mounted on a body 1 of the door lock assembly. The engagement or connection (indicated by 4 in FIGS. 8 and 9) of the lock lever 2 with the sub lever 3 is attained by slidably inserting an end portion of the sub lever 3 into a buffer 5 on a flange portion 2a of the lock lever 2. A connection 7 between a flange portion 2b of the lock lever 2 and a drive rod 6, a transmitting member, is provided above (front side in FIG. 8 and below in FIG. 9) said connection 4 between the lock lever 2 and the sub lever 3 where the connection 7 overlaps the connection 4. With this arrangement, when the drive rod 6 is operated, the lock lever 2 and the sub lever 3 oscillate between the lock and release position.
In such a conventional link coupling arrangement for the vehicle door lock assembly, however, the connection for the transmitting member is provided at a separate position from the connection between the two transmission link members. This requires a space for the connection for the transmitting member in addition to the space for the connection between the two transmission link members. Therefore, the entire door lock assembly is bulky and the structure of the assembly is complicated, preventing reduction in size of and simplification of the door lock assembly.
In particular, when the door lock assembly is used as a lock assembly for a rear door as illustrated in FIGS. 8 and 9, it is very important to reduce the thickness of the door lock assembly as much as possible, to reserve a sufficient space between a window glass 8 of the rear door and the door lock assembly within a limited space.
In the conventional door lock assembly as described above, however, the connection 7 for the drive rod 6 is provided in a different position in the thickness direction of the rear door from the connection 4 between the lock lever 2 and the sub lever 3. Consequently, the body 1 of the door lock assembly is thick and it is difficult to reduce the thickness of the body 1 of the door lock assembly.
To reduce the thickness of the body 1 of the door lock assembly, the connection 7 for, the drive rod 6 may be placed in a lower position (back side in FIG. 8 and upper in FIG. 9) as shown by an arrow A in FIG. 8, in which position the connection 7 is in a non-overlapping position with respect to the connection 4, without moving the position of the rocking center, or a pivot, of the lock lever 2. In this case, deviation or shaking of an axis (indicated by a dot-and-chain line in FIG. 8) of the drive rod 6 becomes larger as the connection 7 is drawn by the drive rod 6, so that the operating force or stroke can not effectively be used. As a result of this, the operation efficiency of the driving rod 6 are lowered.
To reduce the thickness of the body 1 of the door lock assembly, without lowering the operating efficiency of the drive rod 6, the rocking center of the lock lever 2 should be moved together with the connection 7. In this case, however, the body 1 of the door lock assembly should be larger in the width direction though the body 1 of the door lock assembly can be thinner. Thus, the entire size of the body 1 of the door lock assembly can not be reduced again.
In the conventional structure as described above, the buffer 5 is provided on the flange portion 2a of the lock lever 2 and a rod holder 9 is provided in the flange portion 2b of the lock lever 2. This arrangement makes the structure complicated and increases the cost of fabrication. Furthermore, when it is necessary to replace the buffer 5 by a new one after the fabrication, it is very difficult to remove the buffer 5 from the connection 4.